Takes heidi's cats about seven days to finish a 3.5-pound bag of cat food. which is the best estimate of the number of pounds of cat food heidi's cats eat in one year?

In this question it is already given that Heidi's cats takes about 7 days to finish 3.5 pound bag of cat food. Based on this given fact the answer to the question can be easily determined. The number of pounds the cats will eat in a year has to be determined.
We already know that
1 year = 365 days
Then
Heidi's cats in 7 days approximately eats = 3.5 pounds
So
Heidi's cats in 1 year or 365 days will eat = (3.5/7) * 365 pounds
                                                                   = 365/2 pounds
                                                                   = 182.5 pounds
So Heidi's cats will eat approximately 182.5 pounds in 1 year. I hope this is the answer you were looking for.